During deletion in the write-back phase, we do not necessarly need
to check with HasOwnProperty before calling DeleteProperty. Since this
is observable behavior when using proxies, we remove the HasOwnProperty
check to mirror more closely what Spidermonkey does.

R=jgruber@chromium.org

Change-Id: I67768b1d8b13e695b956b2fa0624dcb28fd0664d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1809366Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63866}